Human error in both cases, though both involved incomplete charts (the ridge the Connecticut hit was uncharted but there were all kinds of command/procedure errors that contributed to hitting it [and a number of significant command/procedure problems involving the ship in the months prior to the collision], the seamount the San Francisco hit in 2005 was marked as a possible hazard on charts the crew had but not the one used for navigation and the notation wasn't transferred to the charts used for navigation.)